Why are genetic medical technologies going to remain exclusive to the rich any more than prior revolutionary medical technologies like vaccines, hormonal birth control, or antibiotics? Genetic technologies in general have undergone prolonged cost decreases that don't look to be anywhere near exhausted. Patents restrict access for a couple of decades at most. If the enabling technology is affordable and patents are expired, I see no reason that genetic technology use cannot become widespread.
"Not dying of infectious diseases in childhood" used to be a luxury of the rich too, but it didn't ossify into a permanent class marker.